Closest, most intense one we've observed yet.

Back in April, orbiting observatories started picking up the first indications of a gamma-ray burst. By the time observations wrapped up, the event (GRB 130427A) produced the largest outpouring of photons of any yet detected, and it set a record for the highest energy photon we've seen from these events. And because it was unusually close to Earth, GRB 130427A provided a wealth of information about these extreme events—and told us that we don't really understand how they produce the gamma-rays that are their signature.

Yesterday's issue of Science contains four papers that describe the event, partly because it was unusually well-documented. The enormous stars that produce gamma-ray bursts were much more common in the early Universe and, as a result, most of them occur out at the edge of the observable Universe. But GRB 130427A is an exception; the Universe was already about 10 billion years old when it happened, meaning the supernova that produced the gamma rays occurred less than four billion light years from Earth. As a result, ground-based instruments that were directed to the right area of the sky by the orbiting instruments were quickly able to identify the supernova involved (SN 2013cq).

Meanwhile, the orbiting observatories like SWIFT and Fermi continued to track the event as it occurred. The data they gathered showed that GRB 130427A was an impressive event. At lower energies, it showed a characteristic initial burst followed by a pause of several seconds. The pause ended with a long and complex series of emissions that lasted for roughly 10 seconds, after which there was a gradual tailing off of activity. At the highest energies, however, there was a steady buzz of activity from five seconds out to at least 30, and gamma rays continued to be detected out to 20 hours, setting a record for these events

The record-setting photon, at 95GeV, was actually detected several minutes after the initial outburst. Due to the amount of redshifting that occurred during its billions of years of travel, it actually arrived at a much lower energy than when it was first produced; calculations suggest it was initially 128 GeV.

And that causes a problem for our model of how a gamma-ray burst operates. The model posits that the first burst of radiation signaling that the supernova has started is caused by the matter being rocketed out of the explosion at nearly the speed of light. The larger burst that follows is caused by that matter slamming into material that the star had shed prior to its death, creating a massive shock wave. This slowly fades as the shockwave propagates into the material and the remains of the star start to lose energy through these interactions.

In general, it's a nice explanation for the overall pattern of emissions and what we see at optical wave lengths and on the lower side of the energy spectrum. But things start to go wrong in the details. One paper notes that the initial pulse of photons, thought to come from the material shot out from the explosion, appears to come from a region larger than the shock radius of the explosion, decays in an unexpected way, and is distributed in an unusual manner. It's possible to get the models to handle one of these oddities, but "it is a challenge to explain all these behaviors simultaneously."

Meanwhile, there are also issues with the extended high-energy emissions, which are thought to be generated by synchrotron radiation, photons released as charged particles that lose energy while traveling along a curved path. (synchrotron radiation is so named because the photons were first noticed in early particle accelerators called synchrotrons.) The interactions between the ejected material and the surrounding medium are thought to provide charged particles that travel a curved path through the turbulent environment, which neatly explains the high energy photons.

Except it doesn't. According to the model, there should be a relatively narrow window in which the energies are high enough to produce the sorts of hard gamma rays seen in this explosion. Instead, the burst continued to produce high-energy photons (including the record setter) well after that window should have been shut. The authors point out that other processes could still produce these photons (they mention magnetic reconnection and inverse Compton scattering), but the synchrotron radiation is probably out.

None of this means that the model described earlier is completely wrong, just that there are details it doesn't include or mis-estimates that are critical for understanding our observations.

In any case, it may take another relatively nearby explosion of this sort—one that can give us so many high-quality observations—to sort out the details. The only problem? It's estimated that we'll only see one explosion this close about every 60 years.

Promoted Comments

The larger burst that follows is caused by that matter slamming into material that the star had shed prior to its death, creating a massive shock wave

I doubt I can google an answer to this that I will understand, so I'll let my ignorance shine through:How long prior to a burst does this shedding occur?It seems like our expectations on behavior are predicated on that earlier material being in the way.Is it possible for some external body to have stripped all or some of the earlier shed material away prior to the burst? At least on our side such that it had a clear shot at us? Or that such material may not have been shed uniformly, so there was an opening in the "shell"? Or some lower energy event that blew a hole prior, but wasn't detectible 4 billion ly away? Or just turbulence in the material that gave us a once in a lifetime clear view?

GRBs are likely to be associated with Wolf-Rayet stars, which shed their outer layers for thousands of years. The so-called 'planetary nebulae' are the result. In the final millisecond of the life of these stars, the core collapses; it takes a much longer time for the rest of the star to figure this out (like Wiley Coyote stepping off a cliff), then it all comes crashing down. If the star is rotating rapidly enough, a window to the collapsed center opens up along the axis of rotation (supported by centrifugal force), allowing the intense energy in the core to escape as a GRB. (I am a Gamma-Ray Astronomer)

I can't imagine an energy output descriptive model that includes the formation of a variably-sized black hole. Of course, I'm also not an astro-physicist, and even THEY might not know what kind of space-time warping occurs during that formation period, and how that warping might affect the energy signatures observed 4 billion light years away.

I always like to imagine that at least some of these galactic events we witness are not naturally caused but its super advanced civilizations running various experiments.

Maybe it was a broadcast.

Quote:

At lower energies, it showed a characteristic initial burst followed by a pause of several seconds.

That's the "look over here and prepare for transmission" signal.

Quote:

The pause ended with a long and complex series of emissions that lasted for roughly 10 seconds

That was actually 10 exabytes of data, the aliens' version of Wikipedia, transmitted at gamma ray frequencies of 10 exabits/second. They turned their star into a one-time-use transmitter, but we missed it.

so when the stars fuel is gone the outward pressure of the fusion reaction stops, this causes the star to begin to collapse , in a smal star this leads to the cores density to increases rapidly and heat up until it can’t shrink anymore (white dwarf/neutron star ), the in falling matter (from the rest of the star) crashes into the core and a chock wave starts to move outwards.this chock-wave ignites a fusion burn of all the remaining nuclear fuel in the outer layers and eject massive amount of matter, and thats basically a supernova.so when the star is big the new neutron star at the center of the supernova will have matter thats falls back att it and pushes it over a limit and a black hole is born.

so in massiv stars the core continues to directly collapse into a blackhole , however because the blackhole has so small surface area there is going to be a traffic jam of the matter falling in, slowing down the collapse , the old explanation was that the matter falling in along a curved path(turbulence from traffic jam) and that the blackhole is rotating causing a relativistic jet and synchrotrons radiation leading to gamma ray burst. if this explanation is wrong.why can’t the gamma ray be caused from the traffic jam itself and act like a ever increasing energy pump from pair production resulting in a feedback loop, but because its already ner the event horizon it can’t escape . where am i wrong?

The larger burst that follows is caused by that matter slamming into material that the star had shed prior to its death, creating a massive shock wave

I doubt I can google an answer to this that I will understand, so I'll let my ignorance shine through:How long prior to a burst does this shedding occur?It seems like our expectations on behavior are predicated on that earlier material being in the way.Is it possible for some external body to have stripped all or some of the earlier shed material away prior to the burst? At least on our side such that it had a clear shot at us? Or that such material may not have been shed uniformly, so there was an opening in the "shell"? Or some lower energy event that blew a hole prior, but wasn't detectible 4 billion ly away? Or just turbulence in the material that gave us a once in a lifetime clear view?

I always like to imagine that at least some of these galactic events we witness are not naturally caused but its super advanced civilizations running various experiments.

Maybe it was a broadcast.

Quote:

At lower energies, it showed a characteristic initial burst followed by a pause of several seconds.

That's the "look over here and prepare for transmission" signal.

Quote:

The pause ended with a long and complex series of emissions that lasted for roughly 10 seconds

That was actually 10 exabytes of data, the aliens' version of Wikipedia, transmitted at gamma ray frequencies of 10 exabits/second. They turned their star into a one-time-use transmitter, but we missed it.

Surely the aliens would have waited for an SYN/SYN-ACK. Otherwise they'd be burning through their intergalactic data plans pretty quickly.

Hmm good point. I wonder, can this photon decay into other particles? Can it decay into the higgs? If not, why not? If it can why did it make it all the way to earth?

I am not a physicist, but I think the answer to your question is that a photon cannot decay into a higgs because a higgs particle has a lot of mass, where as a photon has no mass. All particles that I am aware of that decay, decay into lighter particles. So you cannot have a particle that has no mass, decay into one that does. Finally, the photon is considered to be a fundamental particle of the universe, and thus does not decay(else, we couldn't see the CMB from the early stages of the universe).

Wow - shocking - a closer GRB that allows for better observation than the ones being observed at the other edge of the Universe (change in vantage point) rewrites the logic behind what causes them. Who'd've thunk it !!

I always like to imagine that at least some of these galactic events we witness are not naturally caused but its super advanced civilizations running various experiments.

Maybe it was a broadcast.

Quote:

At lower energies, it showed a characteristic initial burst followed by a pause of several seconds.

That's the "look over here and prepare for transmission" signal.

Quote:

The pause ended with a long and complex series of emissions that lasted for roughly 10 seconds

That was actually 10 exabytes of data, the aliens' version of Wikipedia, transmitted at gamma ray frequencies of 10 exabits/second. They turned their star into a one-time-use transmitter, but we missed it.

Surely the aliens would have waited for an SYN/SYN-ACK. Otherwise they'd be burning through their intergalactic data plans pretty quickly.

No, they were transmitting using UDP.

If they'd use TCP/IP the delay loop would have really throttle bandwidth.

Hmm good point. I wonder, can this photon decay into other particles? Can it decay into the higgs? If not, why not? If it can why did it make it all the way to earth?

I am not a physicist, but I think the answer to your question is that a photon cannot decay into a higgs because a higgs particle has a lot of mass, where as a photon has no mass. All particles that I am aware of that decay, decay into lighter particles. So you cannot have a particle that has no mass, decay into one that does. Finally, the photon is considered to be a fundamental particle of the universe, and thus does not decay(else, we couldn't see the CMB from the early stages of the universe).

E=mc^2 allows photons and massive particles to convert into each other; and photons do do it, but need to interact with another particle to do so; also you have to produce (at least?) a pair of particles not just one in order to keep everything conserved.

I always like to imagine that at least some of these galactic events we witness are not naturally caused but its super advanced civilizations running various experiments.

Maybe it was a broadcast.

Quote:

At lower energies, it showed a characteristic initial burst followed by a pause of several seconds.

That's the "look over here and prepare for transmission" signal.

Quote:

The pause ended with a long and complex series of emissions that lasted for roughly 10 seconds

That was actually 10 exabytes of data, the aliens' version of Wikipedia, transmitted at gamma ray frequencies of 10 exabits/second. They turned their star into a one-time-use transmitter, but we missed it.

The larger burst that follows is caused by that matter slamming into material that the star had shed prior to its death, creating a massive shock wave

I doubt I can google an answer to this that I will understand, so I'll let my ignorance shine through:How long prior to a burst does this shedding occur?It seems like our expectations on behavior are predicated on that earlier material being in the way.Is it possible for some external body to have stripped all or some of the earlier shed material away prior to the burst? At least on our side such that it had a clear shot at us? Or that such material may not have been shed uniformly, so there was an opening in the "shell"? Or some lower energy event that blew a hole prior, but wasn't detectible 4 billion ly away? Or just turbulence in the material that gave us a once in a lifetime clear view?

GRBs are likely to be associated with Wolf-Rayet stars, which shed their outer layers for thousands of years. The so-called 'planetary nebulae' are the result. In the final millisecond of the life of these stars, the core collapses; it takes a much longer time for the rest of the star to figure this out (like Wiley Coyote stepping off a cliff), then it all comes crashing down. If the star is rotating rapidly enough, a window to the collapsed center opens up along the axis of rotation (supported by centrifugal force), allowing the intense energy in the core to escape as a GRB. (I am a Gamma-Ray Astronomer)

GRBs are likely to be associated with Wolf-Rayet stars, which shed their outer layers for thousands of years. The so-called 'planetary nebulae' are the result. In the final millisecond of the life of these stars, the core collapses; it takes a much longer time for the rest of the star to figure this out (like Wiley Coyote stepping off a cliff), then it all comes crashing down. If the star is rotating rapidly enough, a window to the collapsed center opens up along the axis of rotation (supported by centrifugal force), allowing the intense energy in the core to escape as a GRB. (I am a Gamma-Ray Astronomer)

I am by no means an astrophysicist, so I can't make much sense of the articles, but I don't understand the significance of a few minutes' or hours' difference in our observations of single photons from an event that occurred billions of years ago. Is it not possible that the one ridiculously energetic photon was sent off in another direction and had its course changed by gravitational lensing? It would then arrive later than would be expected by the model.

I guess I would expect gravitational lensing by objects in the intervening billions of light years to sort of smear the whole event across time equally, and it's the aggregate relations of these events (e.g. the timing of the low energy emissions relative to the high energy ones) that don't match the model.

The larger burst that follows is caused by that matter slamming into material that the star had shed prior to its death, creating a massive shock wave

I doubt I can google an answer to this that I will understand, so I'll let my ignorance shine through:How long prior to a burst does this shedding occur?It seems like our expectations on behavior are predicated on that earlier material being in the way.Is it possible for some external body to have stripped all or some of the earlier shed material away prior to the burst? At least on our side such that it had a clear shot at us? Or that such material may not have been shed uniformly, so there was an opening in the "shell"? Or some lower energy event that blew a hole prior, but wasn't detectible 4 billion ly away? Or just turbulence in the material that gave us a once in a lifetime clear view?

GRBs are likely to be associated with Wolf-Rayet stars, which shed their outer layers for thousands of years. The so-called 'planetary nebulae' are the result. In the final millisecond of the life of these stars, the core collapses; it takes a much longer time for the rest of the star to figure this out (like Wiley Coyote stepping off a cliff), then it all comes crashing down. If the star is rotating rapidly enough, a window to the collapsed center opens up along the axis of rotation (supported by centrifugal force), allowing the intense energy in the core to escape as a GRB. (I am a Gamma-Ray Astronomer)

This is why I like ars. Experts in the field we are discussing willing to step in and shed their outer core as GRB to enlighten us with 128 gEV photons of knowledge.

"Wolf-Rayet stars, which shed their outer layers for thousands of years" poorly named, should be named for my cat.

GRBs are likely to be associated with Wolf-Rayet stars, which shed their outer layers for thousands of years. The so-called 'planetary nebulae' are the result. In the final millisecond of the life of these stars, the core collapses; it takes a much longer time for the rest of the star to figure this out (like Wiley Coyote stepping off a cliff), then it all comes crashing down. If the star is rotating rapidly enough, a window to the collapsed center opens up along the axis of rotation (supported by centrifugal force), allowing the intense energy in the core to escape as a GRB. (I am a Gamma-Ray Astronomer)

Hmm good point. I wonder, can this photon decay into other particles? Can it decay into the higgs? If not, why not? If it can why did it make it all the way to earth?

I am not a physicist, but I think the answer to your question is that a photon cannot decay into a higgs because a higgs particle has a lot of mass, where as a photon has no mass. All particles that I am aware of that decay, decay into lighter particles. So you cannot have a particle that has no mass, decay into one that does. Finally, the photon is considered to be a fundamental particle of the universe, and thus does not decay(else, we couldn't see the CMB from the early stages of the universe).

Nice. One of the best, nicest answers ever. And he gets a single vote; a downvote. Heh.

If that's not proof of how stupid, pointless, and counterproductive voting on comments is.. Well the proof is right there in everybody's face.

Hmm good point. I wonder, can this photon decay into other particles? Can it decay into the higgs? If not, why not? If it can why did it make it all the way to earth?

I am not a physicist, but I think the answer to your question is that a photon cannot decay into a higgs because a higgs particle has a lot of mass, where as a photon has no mass. All particles that I am aware of that decay, decay into lighter particles. So you cannot have a particle that has no mass, decay into one that does. Finally, the photon is considered to be a fundamental particle of the universe, and thus does not decay(else, we couldn't see the CMB from the early stages of the universe).

This is correct: decay (as we currently understand it) can only occur in massive particles. For one thing: photons experience no time (due to being massless, their "frame" insofar as they can even be said to have a frame experiences infinite time dilation), so even if it was possible for them to decay, in our frame their half-life would be infinite.

How high of energies can be expected for the particle-particle interactions in supernovae of this sort? On the order of one of our particle accelerators? Can supernovae create the sorts of short-lived quark-gluon soups we see in particle accelerators, but at a massive scale?

Also, can photons get energy boosts through gravitational slingshots, like our deep space probes do? I imagine it would require a close encounter with a singularity for an observable energy boost , but is it possible?

On the subject of photon energies, what does the spectrum of a GRB look like?One broad peak like blackbody radiation? A series of lines like atomic emission spectra? Or something in between, with a series of broad peaks like molecular UV/visible spectra? (Shifted to tiny wavelengths, of course)

The larger burst that follows is caused by that matter slamming into material that the star had shed prior to its death, creating a massive shock wave

I doubt I can google an answer to this that I will understand, so I'll let my ignorance shine through:How long prior to a burst does this shedding occur?It seems like our expectations on behavior are predicated on that earlier material being in the way.Is it possible for some external body to have stripped all or some of the earlier shed material away prior to the burst? At least on our side such that it had a clear shot at us? Or that such material may not have been shed uniformly, so there was an opening in the "shell"? Or some lower energy event that blew a hole prior, but wasn't detectible 4 billion ly away? Or just turbulence in the material that gave us a once in a lifetime clear view?

GRBs are likely to be associated with Wolf-Rayet stars, which shed their outer layers for thousands of years. The so-called 'planetary nebulae' are the result. In the final millisecond of the life of these stars, the core collapses; it takes a much longer time for the rest of the star to figure this out (like Wiley Coyote stepping off a cliff), then it all comes crashing down. If the star is rotating rapidly enough, a window to the collapsed center opens up along the axis of rotation (supported by centrifugal force), allowing the intense energy in the core to escape as a GRB. (I am a Gamma-Ray Astronomer)

GRBs are likely to be associated with Wolf-Rayet stars, which shed their outer layers for thousands of years. The so-called 'planetary nebulae' are the result. In the final millisecond of the life of these stars, the core collapses; it takes a much longer time for the rest of the star to figure this out (like Wiley Coyote stepping off a cliff), then it all comes crashing down. If the star is rotating rapidly enough, a window to the collapsed center opens up along the axis of rotation (supported by centrifugal force), allowing the intense energy in the core to escape as a GRB. (I am a Gamma-Ray Astronomer)

Which poses a question. Are those two fire blooms moving? Have we been able to see any change since we've had that kind of resolution? They are assumed to be moving outward; expanding; right?

(Okay, a hundred questions. But I held it to three..)

I'm not sure if they're moving fast enough to make noticeable changes since we've began high resolution imaging; but they date back the the mid 19th century when it flared in luminosity and dumped a bunch of its outer layer.